We have demonstrated that delta 9 tetrahydrocannabinol (delta 9 THC), the major psychoactive ingredient of marijuana, causes a unique behavioral effect (convulsions) in a specially bred colony of rabbit (Uaz:NZW-thc). This convulsive trait is inherited by single autosomal recessive mechanism in these tetrahydrocannabinol seizure susceptible (SS) rabbits. The (i.v.) doses of delta 9 THC that cause these rabbit convulsions are comparable to those doses of delta 9 THC that are known to produce psychoactivity (the "high") in humans. Moreover, marijuana cannabinoids that are known to be psychoactive in humans cause convulsions in our SS rabbits. Human non-psychoactive cannabinoids, and hallucinogenic drugs that are not cannabinoids, do not cause convulsions in SS rabbits. Further, delta 9 THC and other psychoactive cannabinoids do not cause convulsions in other populations of "normal" (SR) rabbits, or for that matter, in any animal species that have been tested. Following daily adminstration of delta 9 THC, tolerance of the rabbit convulsions occurs; correspondently, tolerance to the "high" is known to occur following daily delta 9 THC adminstration in humans. Considering the overall correlations of cannabinoid effects in SS rabbits and in humans, the respective rabbit convulsions and the human "high" appear to represent a similar stimulatory mechanism in the brain. It is hypothesized that the SS rabbit represents a unique laboratory animal model of cannabinoid psychoactivity that is available for the study of many unanswered questions concerning marijuana. For example, the rabbit model might predict the human abuse potential of the multitudinous compounds found in the marijuana plant and related compounds synthesized in the laboratory. It might also predict the abuse potential of different strains or varieties of crude marijuana that are encountered throughout the world. It is conceivable that studies in the SS rabbit could yield information on where and how marijuana is acting in the brain. Further, studies of long-term effects of marijuana in SS rabbits (including pregnant female and neonatal and adolescent offspring) could yield relevant findings that may apply to long term marijuana effects in humans.